Format tag slugs in readme.md

[kasparsd]

The readme convertor is converting all plugin tags into links but it doesn't format the tag slut to replace spaces with dashes. This results in broken links:

https://github.com/georgestephanis/two-factor/blob/330e36a09c1f744e176275bf42fd7b07b5f2d09a/readme.md

We should replace all spaces with slashes here:

wp-dev-lib/class-wordpress-readme-parser.php

Lines 156 to 164 in cb1dd85

	$formatted_metadata['Tags'] = join(
	', ',
	array_map(
	function ( $tag ) {
	return sprintf( '[%1$s](https://wordpress.org/plugins/tags/%1$s)', $tag );
	},
	$this->metadata['Tags']
	)
	);